成品油管道投产前内腐蚀原因分析

Internal Corrosion Cause Analysis of a Products Pipeline Before Putting into Operation

采用SEM、EDS和XRD对失效管段进行了宏观腐蚀形貌、微观组织、化学组成和腐蚀产物测试分析,结合管道工况条件和内检测数据,分析了西部某成品油管道投产前内腐蚀成因。结果表明,管线高程起伏较大,试压水清扫不彻底,试压水在管线低洼点残留,水线上下形成的氧浓差电池效应导致水线腐蚀发生,带压封存促进了水线腐蚀的发展。提出了试压后进行深度扫水甚至吹扫干燥,不立即投产,管线进行干燥和注氮封存的保护措施。

Corrosion failure analysis of a west-located product pipeline before putting into operation was carried out in terms of analyzing the inspection corrosion data and the pipeline conditions as well as the macro-morphology observation, microstructure examination, analysis of chemical composition and constituents of corrosion products by means of SEM, EDS and XRD. The results showed that due to the large variation of the pipeline elevation and the insufficient cleaning up of the hydrotest water, thus there existed residual water at some low points of the pipeline. Where, water-line corrosion might occur as a result of oxygen concentration difference cell formed between the upper and lower parts of the water-line.In addition, water-line corrosion was accelerated due to sealed with pressurized air. Therefore, as countermeasure, it is proposed that the pipeline should be completely cleaned up and even dried up by air blowing after hydrotesting, and for the pipeline which was not immediately put into operation, a nitrogen injection sealing should be adopted to avoid such corrosion.